An alternating current (AC) cable usually has three current-carrying core wires respectively connected to a live line, a neutral line, and a ground line of a power supply. The current-carrying core wires are respectively wrapped by an insulating layer, so that any one of the current-carrying core wires is electrically insulated from the others. In addition, the AC cable has an insulating shell for surrounding the current-carrying core wires.
After the conventional AC cable has been used for a long time, a leakage current may occur between the current-carrying core wires due to aging or damage of the insulating films or other factors. The leakage current may cause fire hazard or threaten the personal safety, which should be avoided as much as possible. The prior art provides the following solutions to detect the leakage current leaking from the current-carrying core wires out of the insulating films.
In the prior art, the most direct solution is to employ a current leakage detection metal net, of which the coverage rate is greater than or equal to 85%. However, due to the high coverage rate of the current leakage detection metal net, the prior art employing the current leakage detection metal net is associated with high cost. It is noted that, the prior art of high cost cannot be solved by reducing the coverage rate of the current leakage detection metal net because lower coverage rate may result in poor leakage current detection effects.
Chinese Patent Application No. CN200520063686.5, entitled “SCREENED CABLE”, discloses a kind of screened cable, as shown in FIG. 1, which includes three current-carrying core wires A, three insulating films B, two screen nets D, and an outer insulating sheath E. The current-carrying core wires A are respectively connected to a live line, a neutral line, and a ground line of a power supply, and are electrically insulated from one another through the insulating films B. The screened cable is characterized in that: a shielding thin film C is disposed between the insulating layer B and the screen net D on each of the current-carrying core wires A connected to the live line and the neutral line. The current-carrying core wire A, the insulating layer B, the shielding thin film C, the screen net D, and the outer insulating sheath E are arranged sequentially from inside to outside.
Chinese Patent Application No. CN200720173349.0, entitled “POWER SUPPLY LINE WITH ELECTRIC LEAKAGE TESTING CONDUCTOR”, discloses a power supply line with an electric leakage testing conductor feature. The power supply line includes three current-carrying core wires and one electric leakage testing conductor for detecting a current leakage phenomenon. Each current-carrying core wire is wrapped by an insulating layer on an outer surface thereof. Two current-carrying core wires are selected from the current-carrying core wires, and the insulating layer of each selected current-carrying core wire is further wrapped by a metal conductive layer. The electric leakage testing conductor for detecting the current leakage phenomenon is electrically connected to the metal conductive layers. The power supply line has an outermost insulating layer for wrapping the two selected current-carrying core wires and the electric leakage testing conductor.
Chinese Patent Application No. CN200720149261.5, entitled “POWER CABLE HAVING METAL FOIL FOR DETECTING LEAKAGE CURRENT”, discloses a power cable having a metal foil which is used for detecting a leakage current. The power cable is formed by two current-carrying core wires, two insulating films respectively wrapping the two current-carrying core wires, and an outermost insulating layer wrapping the current-carrying core wires and the insulating films. The power cable is characterized in that: the outer surfaces of the insulating films of the two current-carrying core wires are respectively wrapped by a metal foil for detecting leakage current, and the outer surfaces of the metal foils are respectively covered with a sparse metal woven net, of which the coverage rate is 2%. That is, firstly, the thin metal foils wrap the outer surfaces of the insulating films of the two current-carrying core wires, and then the sparse metal woven nets wrap the metal foils, so as to reduce the cost of the power cable.
By using the thin foils to save material cost, it is associated with problems, like being brittle of fragile. Furthermore, in most cases, such thin metal foils can only be spread in a plane, but not suitable for being coiled. Therefore, under the current technical level, it is quite difficult to wrap a single layer of the thin metal foil on the surface of the insulating layer for current-carrying core wire. Even if the single layer of the thin metal foil is wrapped on the surface of the insulating layer of the current-carrying core wire at an extremely high technical cost, the metal foil is still easily broken due to the bending or folding of the current-carrying core wire during the use of the power cable. Apparently, the problem can be solved by using the thick metal foils. However, this method of having thicker metal foils does not meet the intention of cost-saving, and further increases the weight of the power cable.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.